Guided by theories of cultural participation, the authors examined mother-child, father-child, and triadic interactive behaviors in 141 Israeli and Palestinian couples and their firstborn child at 5 and 33 months as antecedents of children’s social competence. Four parent-child measures (parent sensitivity, child social engagement, parental control, dyadic reciprocity) and two family-level measures (cohesion and rigidity) were coded at each age. Children’s social competence was observed at child-care locations. Cultural differences were observed for parent sensitivity and child social engagement, and the large cultural differences in sensitivity observed in infancy were attenuated by the toddler age. Interactive behaviors correlated with culture-specific parenting practices, child-rearing goals, and sex-role attitudes. Mother-child reciprocity in infancy and child engagement with father and family-level cohesion at both time points predicted social competence. Maternal sensitivity in infancy facilitated social competence only among Israeli children. Paternal control in toddlerhood interfered with Israeli children’s social functioning but contributed to competence among Palestinians. Results underscore the links between early relational experiences and children’s adaptation to the social milieu.